The present invention relates to an electrical machine with a first active part, on which at least one electromagnet and at least one permanent magnet are fitted, and a second active part, which has a large number of pole teeth and which interacts magnetically with the first active part.
Linear motors typically have the design as is reproduced schematically in FIG. 1. A primary part 1 is capable of moving over a secondary part 2 in the travel direction 3. The primary part has teeth 4 which are of uniform width and are spaced apart uniformly. A coil 5 is wound around each of these teeth 4. This is referred to as concentrated coils in the primary part 1. Such a design of a linear motor has the disadvantage, however, that construction-related harmonics of the magnetic field impair the synchronism of the motor.
In order to avoid this disadvantage, a linear motor has been developed in which the primary part has teeth of different widths. Such a linear motor is sketched in FIG. 2. The primary part 10 in this case has wide teeth 11 and narrow teeth 12. A coil 13 is wound around each wide tooth 11. The secondary part 14 has permanent magnets 15 and therefore has the same construction as the secondary part 2 of the linear motor in FIG. 1. A torque motor of this type with a small tooth between the coils is described, inter alia, in the documents DE 101 24 415 A1 and DE 102 48 771 A1.
One disadvantage of the linear motors in FIG. 1 and FIG. 2 consists in the fact that the secondary part is complex in terms of manufacture and expensive permanent magnets are required along the entire travel path.